1. Field of the Invention
The present invention relates generally to railroad track switch mechanisms and, more particularly, to a sensor apparatus for sensing the position of a railroad track point.
2. Description of the Related Art
As is known in the relevant art, railroad switch mechanisms are employed between a first set of railroad tracks and an intersecting second set of railroad tracks to selectively switch a train traveling on one of the sets of tracks to the other set of tracks. At the switch mechanism, each pair of track includes a stock rail that is fixed and a movable rail that is selectively movable by the switch mechanism. In this regard, the two movable rails are connected with one another by a bar that permits both movable rails to be simultaneously moved in a single motion of the switch machine. Most switch machines today include an electric motor that performs the switching operation, as well as a backup lever that permits the tracks to be switched manually.
The movable tracks are selectively shifted between a first desirable position and a second desirable position with regard to the fixed stock rails. In the first desirable position, a first movable rail is disposed closely adjacent a first stock rail and the second movable rail is spaced from the second stock rail. In the second desirable position, the second movable rail is disposed closely adjacent the second stock rail, and the first movable rail is spaced from the first stock rail. Each of the movable rails is tapered to a sharp point where it engages the corresponding stock rail in order to provide a smooth transition from the stock rail to the movable rail.
In order to maintain such a smooth transition between the stock rail and the movable rail, it is desired that the movable rail with its tapered end be disposed against the stock rail or at least be disposed closely adjacent the stock rail and typically be spaced no farther than xc2xc inch away from the stock rail. If the movable rail is spaced more than xc2xc inch away from the stock rail, it is possible for the train wheel rolling along the stock rail to miss the movable rail and continue along the stock rail which can result in a derailment of the train.
In an effort to avoid such a derailment situation, it is known to provide a system for detecting the position of the point of the movable track and to send an appropriate signal depending upon whether the movable track point is within the typical xc2xc inch threshold or is outside the threshold and in need of readjustment. For instance, the system may display a green light that can be observed by train personnel if the track point is within the threshold, and alternatively display a red light if the track point is outside the threshold and in need of adjustment. In the latter situation, the train is expected to stop and wait while a railroad worker travels to the switch site and readjusts the movable tracks within the threshold to permit the train to safely pass. While such a delay is costly, it advantageously avoids a train derailment. Previously known point detection systems have not, however, been without limitation. Most such known detection systems have employed mechanical apparatuses such as cam and roller arrangements that were configured to engage certain parts of a specially ground point detector bar that was physically connected with the movable tracks. The cam and roller arrangements would engage special surfaces of the point detector bar when the point detector bar and thus the movable tracks were in specific positions with respect to the stock rails. Such mechanical point detection systems were subject to high levels of wear over time with consequent lost motion and inaccurate position readings. Additionally, in the event that such mechanical detection systems were maladjusted with the cam and roller arrangements being in perpetual engagement with the point detector bar, such maladjustment resulted in accelerated wear due to the vibrations experienced by the system when a train passed over the switch. It thus is known to provide an electronic sensor that is capable of detecting the position of the track point without requiring physical contact between mechanical components.
Such known sensor-based systems have not, however, been without limitations. Due to the high vibrations and the extreme temperature variations of the environment in which such sensor-based systems are used, it is known that the sensitive sensing equipment of such systems periodically requires replacement. Such replacement can be time consuming inasmuch as it can require complex disassembly of the switch machine and painstaking readjustment procedures. It is thus desirable to provide a point detector system that can be easily replaced. It is further desired to provide a sensor system that can readily be readjusted.
Previously known sensor-based systems have been generally effective at indicating that a track point has become maladjusted and impassable thus requiring a train to await readjustment of the track point before proceeding over the switch. Such waiting is costly for the rail company, however. It thus is desirable to additionally provide a sensor-based point detection system that additionally indicates the need for imminent readjustment of a track point prior to the time that the track point actually becomes maladjusted and is in need of immediate readjustment.
In view of the foregoing, a modular sensor apparatus for detecting the location of a movable track point includes a primary sensor and a secondary sensor disposed on a sensor mount that is movable with respect to a frame that is mounted on a switch machine. The secondary sensor is offset from the primary sensor in order to permit the secondary sensor to detect the need for imminent readjustment of the track point prior to the time at which the track point becomes maladjusted and in need of immediate readjustment. The sensor mount is threadably adjustable with respect to the frame, whereby once the primary sensor has detected the position of the movable track point when it is disposed against a fixed stock rail, the sensor mount can be moved a fixed threshold distance by rotating a thumbwheel a fixed number of turns.
An aspect of the present invention is to provide a sensor apparatus for detecting the location of a movable track point of a movable track of a railroad switch machine.
Another aspect of the present invention is to provide a sensor apparatus that is modular.
Another aspect of the present invention is to provide a sensor apparatus having a primary sensor and a secondary sensor, the secondary sensor being offset from the primary sensor.
Another aspect of the present invention is to provide a sensor apparatus that detects the need for imminent readjustment of a track point prior to the track point becoming maladjusted and requiring immediate readjustment.
Another aspect of the present invention is to provide a sensor apparatus having a threadably adjustable sensor mount that can be adjusted a threshold distance by rotating a threaded member a given number of turns.